#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N,L,K;
int A[202020];

int TL[202020];
int TR[202020];
int ok(int v) {
	
	TL[0]=1<<30;
	for(int x=0,y=0;x<N;x++) {
		while(A[x]-A[y+1]>=v) y++;
		TL[x+1]=TL[x];
		if(A[x]-A[y]>=v) TL[x+1]=min(TL[x+1],x-y);
	}
	TR[N]=1<<30;
	for(int x=N-1,y=N;x>=0;x--) {
		while(A[y-1]-A[x]>=v) y--;
		TR[x]=TR[x+1];
		if(A[y]-A[x]>=v) TR[x]=min(TR[x],y-x);
		if((N-TL[x]-TR[x]+2)>=K+1) return 1;
	}
	return 0;
	
	
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>L>>K;
	FOR(i,N) cin>>A[i+1];
	A[N+1]=L;
	N++;
	int ret=0;
	for(i=29;i>=0;i--) if(ok(ret+(1<<i))) ret+=1<<i;
	cout<<ret<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}